Nikolaos of Greece, say, not Spartan I suspect! (6,5)
I believe the answer is:
patron saint
'nikolaos of greece' is the definition.
I can't tell whether this defines the answer.
'not spartan i suspect' is the wordplay.
'suspect' indicates an anagram (a suspicious or unusual spelling).
'not'+'spartan'+'i'='notspartani'
'notspartani' is an anagram of 'PATRON SAINT'.
'say' is the link.
Can you help me to learn more?
(Other definitions for patron saint that I've seen before include "Virgin Mary in France possibly" , "National representative" , "Religious guardian" , "Protector in heaven" , "Patrick for Ireland, for example" .)